/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#include "tensorflow/compiler/xla/stream_executor/stream_executor.h"
#include "tensorflow/tsl/platform/test.h"

namespace stream_executor {
namespace {

class StreamTest : public ::testing::Test {
 protected:
  std::unique_ptr<StreamExecutor> NewStreamExecutor() {
    Platform* platform = MultiPlatformManager::PlatformWithName("Host").value();
    StreamExecutorConfig config(/*ordinal=*/0);
    return platform->GetUncachedExecutor(config).value();
  }
};

TEST_F(StreamTest, NoInitNotOk) {
  std::unique_ptr<StreamExecutor> executor = NewStreamExecutor();
  Stream stream(executor.get());
  EXPECT_FALSE(stream.ok());
}

TEST_F(StreamTest, InitOk) {
  std::unique_ptr<StreamExecutor> executor = NewStreamExecutor();
  Stream stream(executor.get());
  stream.Init();
  EXPECT_TRUE(stream.ok());
}

TEST_F(StreamTest, OneSubStream) {
  std::unique_ptr<StreamExecutor> executor = NewStreamExecutor();
  Stream stream(executor.get());
  stream.Init();
  EXPECT_TRUE(stream.ok());

  // Get and return a sub-stream. Sub-streams are always initialized.
  Stream* sub_stream1 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream1->ok());
  stream.ReturnSubStream(sub_stream1);

  // Get and return another sub-stream.
  Stream* sub_stream2 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream2->ok());
  stream.ReturnSubStream(sub_stream1);

  // The underlying sub-streams should be the same, since sub_stream1
  // was returned before we tried to get sub_stream2.
  EXPECT_EQ(sub_stream1, sub_stream2);
}

TEST_F(StreamTest, TwoSubStreams) {
  std::unique_ptr<StreamExecutor> executor = NewStreamExecutor();
  Stream stream(executor.get());
  stream.Init();
  EXPECT_TRUE(stream.ok());

  // Get two sub-streams.
  Stream* sub_stream1 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream1->ok());
  Stream* sub_stream2 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream2->ok());

  // The underlying sub-streams should be different, since neither
  // sub-stream has been returned.
  EXPECT_NE(sub_stream1, sub_stream2);

  // Return sub_stream1 and get sub_stream3, which should be the same.
  stream.ReturnSubStream(sub_stream1);
  Stream* sub_stream3 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream3->ok());
  EXPECT_EQ(sub_stream1, sub_stream3);
  EXPECT_NE(sub_stream2, sub_stream3);

  // Return sub_stream2 and get sub_stream4, which should be the same.
  stream.ReturnSubStream(sub_stream2);
  Stream* sub_stream4 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream4->ok());
  EXPECT_EQ(sub_stream2, sub_stream4);
  EXPECT_NE(sub_stream3, sub_stream4);
}

TEST_F(StreamTest, FailedSubStreamBeforeReturnNotReused) {
  std::unique_ptr<StreamExecutor> executor = NewStreamExecutor();
  Stream stream(executor.get());
  stream.Init();
  EXPECT_TRUE(stream.ok());

  // Get sub_stream1.
  Stream* sub_stream1 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream1->ok());

  // Force an error on sub_stream1; here we call a method that requires DNN
  // support, which we know the Host platform doesn't support.
  sub_stream1->ThenDepthConcatenate({}, {}, nullptr);
  EXPECT_FALSE(sub_stream1->ok());

  // Return sub_stream1 and get sub_stream2.
  stream.ReturnSubStream(sub_stream1);
  Stream* sub_stream2 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream2->ok());

  // The underlying sub_streams should be different. They would have been the
  // same, but since we forced an error on sub_stream1, it will not be
  // re-used. Sadly we can't just check:
  //   EXPECT_NE(sub_stream1, sub_stream2);
  //
  // The above should hold logically, but it may fail if the new Stream instance
  // allocated for sub_stream2 happens to reside in the same memory address as
  // sub_stream1.
  //
  // The check that sub_stream2->ok() serves as a good-enough check.

  // Return sub_stream2 and get sub_stream3. The previous error on sub_stream1
  // has no effect on these streams, and they are the same.
  stream.ReturnSubStream(sub_stream2);
  Stream* sub_stream3 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream3->ok());
  EXPECT_EQ(sub_stream2, sub_stream3);
}

TEST_F(StreamTest, FailedSubStreamAfterReturnNotReused) {
  std::unique_ptr<StreamExecutor> executor = NewStreamExecutor();
  Stream stream(executor.get());
  stream.Init();
  EXPECT_TRUE(stream.ok());

  // Get and return sub_stream1.
  Stream* sub_stream1 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream1->ok());
  stream.ReturnSubStream(sub_stream1);

  // Force an error on sub_stream1; here we call a method that requires DNN
  // support, which we know the Host platform doesn't support.
  //
  // It is a bit weird to use sub_stream1 after it has already been returned. By
  // doing this, we're simulating an asynchronous error that occurs during
  // execution of the sub_stream, that occurs after the sub_stream is returned.
  //
  // E.g. the following is a common pattern of usage, where the execution of the
  // operations enqueued onto the sub streams may occur after the streams have
  // already been returned.
  //
  //   void EnqueueOnSubStreams(Stream* stream) {
  //     Stream* sub_stream1 = stream.GetOrCreateSubStream();
  //     Stream* sub_stream2 = stream.GetOrCreateSubStream();
  //     // ... enqueue some operations on the sub streams ...
  //     stream.ThenWaitFor(sub_stream1).ThenWaitFor(sub_stream2);
  //     stream.ReturnSubStream(sub_stream1);
  //     stream.ReturnSubStream(sub_stream2);
  //   }
  //
  //   Stream* main_stream = ...;
  //   EnqueueOnSubStreams(main_stream);
  //   main_stream.BlockHostUntilDone();
  //
  // TODO(b/112196569): The semantics of failed sub-streams is error-prone;
  // GetOrCreateSubStream can still return a sub-stream that has not encountered
  // an error yet, but will encounter one in the future, based on previously
  // enqueued operations.
  sub_stream1->ThenDepthConcatenate({}, {}, nullptr);
  EXPECT_FALSE(sub_stream1->ok());

  // Get and return sub_stream2.
  Stream* sub_stream2 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream2->ok());

  // The underlying streams should be different. They would have been the same,
  // but since we forced an error on sub_stream1, it will not be re-used. Sadly
  // we can't just check:
  //   EXPECT_NE(sub_stream1, sub_stream2);
  //
  // The above should hold logically, but it may fail if the new stream instance
  // allocated for sub_stream2 happens to reside in the same memory address as
  // sub_stream1.
  //
  // The check that sub_stream2->ok() serves as a good-enough check.

  // Return sub_stream2 and get sub_stream3. The previous error on sub_stream1
  // has no effect on these streams, and they are the same.
  stream.ReturnSubStream(sub_stream2);
  Stream* sub_stream3 = stream.GetOrCreateSubStream();
  EXPECT_TRUE(sub_stream3->ok());
  EXPECT_EQ(sub_stream2, sub_stream3);
}

}  // namespace
}  // namespace stream_executor
